A High Voltage Direct Current (HVDC) breaker is a switching device capable of making, breaking and continuously carrying a DC current at a high voltage. An HVDC breaker is often used as a component in an HVDC system for power transmission.
Since there are no natural zero-crossings of the current or voltage in a direct current system, special attention has to be given to HVDC circuit breaker design. The power transmitted via an HVDC system is typically very high, and can for example be in the order of GW. When breaking the current in an HVDC system with a mechanical interrupter in the HVDC breaker, an arc is built up between the interrupter contacts, which can only be extinguished by forcing a current zero. As the arc has a negative resistance, a resonant circuit has been introduced in order to create artificial current zeros in mechanical HVDC breakers. Furthermore, a non-linear resistor is typically connected in parallel with the resonant circuit. Once the arc current has been forced to zero, the current is commutated to the non-linear resistor, which absorbs the energy of the interruption process and limits the voltage. Known further techniques for facilitating the extinguishing of the arc are the use of an inert gas, such as SF6, or the placement of the interrupter contacts in a vacuum vessel. As an alternative to mechanical HVDC breakers, solid state HVDC breakers are proposed in the art which make use of a power semiconductor switch as interrupter.